Bad service

I being cell customer for morethan 6 year and i was loyal customer now i have a big problem last month they suspend my line when i call them i was told that my account are in erreas i said no i pay cell c every month they said they was the audit when the check i did not pay them january premiur i said i did they ask me for slips i said i dont have a slip for january they said i must pay 620 i did on 7 of august now i try to cancel my cell c rooter now they said i did not pay for january and feb i ask my self how come i can not pay they dont see from jan until August